Troponin complex is a heteromeric protein playing an important role in the regulation of skeletal and cardiac muscle contraction. It consists of three subunits: troponin I (TnI), troponin T (TnT) and troponin C (TnC). Each subunit is responsible for part of troponin complex function; e.g., TnI inhibits the ATP-ase activity of acto-myosin.
TnT and TnI are present in myocardium in different forms than in skeletal muscles. Cardiac TnI (cTnI) is expressed only in myocardium. cTnI has been widely used as a marker of cardiac tissue injury. cTnI is considered to be more sensitive and significantly more specific in the diagnosis of myocardial infarction than CK-MB, myoglobin, and LDH isoenzymes.
cTnI can be detected in patient's blood 3-6 hours after onset of the chest pain, reaching peak level within 16-30 hours. cTnI is also useful for the late diagnosis of acute myocardial infarction, because elevated concentrations can be detected in blood even 5-8 days after onset.
During the incubation in the necrotic muscle after acute myocardial infarction, cTnI is cleaved by endogenous proteases. The most stable fragment resulting from this cleavage is located between 30 and 110 amino acid residues. For this reason, cTnI assays have employed antibodies that recognize this fragment.
In view of the importance of early detection of cardiac tissue injury, there clearly remains a need for methods and kits to identify cardiac pathology, or risk thereof, either as an independent indicator, or which can be employed in conjunction with other assays.
This background information is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.